Witnesses say a male suspect with a semi-automatic handgun entered the store, wearing a bandana over his face, and demanded money from the safe.
He then took off with an undisclosed amount of cash.
None of the restaurant employees were injured in the robbery.
The robber is described as dark skinned, in his late teens or early 20s, 5 feet 8 inches, with a thin build.
Anyone with information about the incident is urged to contact the San Jacinto Police Department at (951) 654-2702.